Cycles image renders in black and white
What are you trying to do with the dilate/erode node?

That is what is turning your image into B&amp;W.

Remove that node and your image is fine:



The Dilate/Erode node expects an input of a single channel (not RGB), and will output a single channel as well: a single channel will be a Black and White image.

The Dilate/Erode's node is mostly used is to expand or contract the edge of masks.

To work with a color image (RGB), you would need to split the channels of the image, and use dilate/erode nodes on each of the channels of the image. Then the channels can be recombined, as in thid example from the blender manual  



But I suspect that you are looking for a way to create some glow... Use the Glare node instead.